MYOBLASTOMAS, NEURAL ORIGIN

Transcription

1 MYOBLASTOMAS, NEURAL ORIGIN REPORT OF SIX CASES, ONE WITH MULTIPLE TUMORS* L. L. ASHBURN, M.D., AND R. C. RODGER, M.D. From the Pathology Service of the U.S. Public Health Service Hospital, Baltimore 11, Maryland In 1926 AbrikossofT 1 reported 5 unusual tumors that he believed to be of muscle origin. In he reported additional cases under the name "myoblastenmyome." In subsequent reports, authors have expressed differences of opinion on the histogenesis of these granular-cell tumors. The concept that they arose from adult skeletal muscle, suggested by Abrikossoff, was later modified to include an origin from embryonal muscle rests. In keeping with this concept of origin, these tumors have commonly been reported under the name "myoblastoma." A few authors in recent years have dissented from this view, pointing out that the transition from muscle fibers to tumor cells was only apparent and that there was no basic similarity between the tumor cells and myoblasts.. Leroux and Delarue in offered the hypothesis that the granular cells were histiocytes storing some as yet unknown substances. This concept has been considered favorably by a few authors. Although never demonstrated, glycogen has been suggested as being the stored substance. Fust and Custer in 1948 and ' 6 after studying a large series of cases concluded that these tumors were of neural origin and proposed the term "granular cell neurofibroma." In a recent paper (1950) Pearse 11 reported the finding of the same histologic relationship between nerves and tumor cells as that described by Fust and Custer. On a histochemical basis, Pearse concluded that the tumor cells represented altered fibroblasts rather than Schwann cells. He assumed that in the Fust and Custer concept the Schwann cell was incriminated and much of his interpretative discussion is on this point. These granular-cell tumors have been reported with increasing frequency in recent years. According to Pearse, 232 had been recorded up to With rare exception these tumors have occurred as single lesions. In a period of one year we observed 5 cases with single tumors and 1 case with 7 tumors. In the present report, brief clinical histories and composite histologic findings of these 6 cases are given together with an evaluation of these findings in relation to the various histogenic concepts. METHODS The tumors were fixed in 10 per cent formalin and sectioned after paraffin embedding. Sections were stained by the following methods: Romanowsky; hematoxylin and eosin; Van Gieson; Bodian protargol; Wilder's reticulum method; periodic acid-schiff routine, with and without diastase digestion, and phosphotungstic-acid hematoxylin. Frozen sections were stained with Sudan * Received for publication, February 11,

2 MYOBLASTOMAS 441 IV (Herxheimer's technic) and Sudan black B (Chiffelle and Putts' propylene glycol procedure). 4 Unstained frozen sections were examined under polarized light for anisotropic substances. CLINICAL HISTORIES Case t. A colored woman of unstated age had had a skin lesion of the right upper chest, near the axilla, for about 6 years. The patient stated that the lesion had not increased in size since the first 6 months. The lesion was somewhat elevated and measured 2 by 2.5 cm. The overlying skin showed no significant variation from normal. The nodule was excised. Case 2. A 41-year-old white man stated that he had had a lump in the skin of the left thigh for many years without appreciable change in size. This cutaneous nodule measured 1 cm. in diameter and was located about 7.5 cm. above the knee anteriorly. The lesion was excised. Case 3. A 46-year-old white man stated that he had had a nodule in his tongue for about 3 months. The nodule was located on the right lateral margin of the tongue, in the middle third. It measured 1 by 0.7 cm. The lesion was white, firm, and not ulcerated. A dental bridge was present at the level of the tongue lesion. This lesion was excised, including a margin of apparently normal tissue. The lesion had not recurred 5 months after excision. Case 4- A 35-year-old white man had noticed a nodule in his right flank approximately 6 weeks before admission to the hospital. The patient stated that the nodule had not increased in size during this period. There was no history of trauma and the lesion was not tender. Examination revealed a hard nodule 1 by 1 by 2 cm. in the subcutaneous tissue in the midaxillary line approximately halfway between the iliac crest and the twelfth rib. It appeared to be partially adherent to the skin but otherwise was movable. The lesion was widely excised. After 4 months there was no evidence of a recurrence. Case 5. A 25-year-old white man was admitted to the hospital with a history of atopic dermatitis since childhood. The dermatitis had recurred at intervals on the face, neck, arms and trunk. Approximately 6 years before admission circumscribed papular lesions developed on the nape of the neck, the right lateral cervical region and the left supraclavicular region. On admission most of the lesions were slightly raised and somewhat lighter in color than the surrounding skin. Thej r were firm and most of them showed some umbilication. One lesion measured 0.7 cm. in diameter; five, between 1.5 and 2 cm.; and one, 2.5 cm. The latter was located on the nape of the neck and had been irritated by the shirt collar. Following excision, there was no evidence of recurrence and no additional lesions appeared in 15 months. Case 6. A 44-year-old white man had a small tender nodule beneath the skin on the volar aspect of the left middle finger. He stated that it had been present for many months and had shown very gradual enlargement. The excised nodule measured 4 mm. in greatest dimension. A number of other skin lesions were removed from this patient; all were interpreted histologically as sclerosing hemangiomas (dermatofibroma lenticulare). There was no evidence of recurrence after 9 months. HISTOLOGIC OBSERVATIONS In view of the numerous recorded histologic descriptions of granular-cell myoblastomas and their remarkable cytologic similarity a description of each tumor will not be given. The following observations are based on the examination of from 8 to 10 sections from each tumor stained by a variety of technics. All the tumors were diagnosed as typical uniform granular-cell myoblastomas. Nine of them were located in the dermis, one in the tongue and two in subcutaneous tissue. Most of the tumors were compactly cellular and moderately well circum-

3 442 ASHBURN AND RODGER scribed. However, in such instances small nests of tumor cells frequently were seen in the surrounding connective tissue; occasionally as much as a few millimeters from the main tumor margin. In 2 tumors this circumscription was less distinct. In 3 others, the tumors did not show a central accumulation of cells. In these, small nests of granular tumor cells were scattered throughout the dermis in the area of involvement and, in a given area, the intervening dermal connective tissue exceeded the aggregate bulk of tumor. Sharp circumscription and pseudoencapsulation were evident in one of the subcutaneous tumors. Intimate association of nerves and tumor cells was observed in 9 of the 12 tumors (5 of 6 cases). This association consisted in most instances of granular cells in the perineurium and apparently expanding it. However, tumor cells intermingled with myelinated nerve fibers were recognized in 5 tumors (Cases 1 and 5). The frequency of neural involvement in a given tumor was quite variable. In some instances from one to several involved nerves were found in each section studied. In a few tumors prolonged search was required before convincing evidence of neural involvement was found. A somewhat more frequent finding was a collar of tumor cells surrounding a myelinated nerve, without demonstrable involvement of the perineurium. In a number of tumors small groups of cells sometimes showed concentric arrangement as though they had been formed within a confining membrane. Two of the dermal tumors from Case 5 showed marked hyperplasia of the overlying stratified squamous epithelium. There were marked hyperkeratosis and moderate patchy parakeratosis. The thickening of the stratum spinosum was irregular, and there were marked elongation and distortion of the rete pegs, which at their tips appeared to fray out into the dermis. In this location, small, apparently isolated, nests of squamous cells were not infrequent. Cells of the rete showed some variation in nuclear size and depth of staining,' and a few cells showed mitoses. An occasional cell was dyskeratotic. Granular tumor cells were present in the connective tissue surrounding the rete. Incompletely formed small pearls were also present. The epithelial changes associated with these two tumors were interpreted as early squamous-cell carcinoma. Slight epithelial hyperplasia was observed in three of the other dermal tumors. In the remainder, the epithelium was normal or slightly atrophic. In studying these tumors attention was especially directed toward included structures blood vessels, erector pili muscles, hair follicles and sweat glands. In no instance were tumor cells seen intimately investing these structures; also, they were never found invading the smooth muscles of the skin. Close alignment with voluntary muscle fibers was observed in the one tumor of the tongue. No suggestion of a transition was observed. FIG. 1 (upper left). Case 1. Intimate admixture of granular cells with myelinated fibers in a small nerve twig. Circumscribed nests of granular cells in the surrounding stroma. Allochrome. X 350. FIG. 2 (upper right). Case 2. Sheets of granular cells surrounding a small nerve and involving the perineurium with fraying of its components. Allochrome. X 830. FIG. 3 (lower left). Case 5. Granular cells in epineurium and perineurium as well as between the latter and the myelinated fibers. Allochrome. X 830. FIG. 4 (lower right). Case 5. Extensive involvement and fraying of the perineurium by granular cells. Allochrome. X 830.

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5 444 ASHBTJRN AND RODGER The cytoplasmic granules of all tumor cells showed' slight to moderate positivity when stained by the periodic acid-schiff (PAS) technic. In addition, sections from each tumor were stained by this technic, following exposure to malt diastase (1 per cent). In each instance the PAS positivity was apparently of equal intensity, indicating the absence of a significant amount of glycogen. Frozen sections stained with Sudan;IV and Sudan black B* showed slight positivity of the tumor-cell granules with the former dye and slight to moderate positivity with the latter. Myelin sheaths in the Sudan-black preparation were stained more deeply than the tumor-cell granules, and neutral fat globules were still more intensely black. Fine lipoid droplets were seen in sweat-gland epithelium. The Sudan-black preparations were particularly helpful in showing nerve-tumor cell relationship. In Van Gieson preparations of the skin tumors there was no evidence of increased collagen. Rather, in those cases where tumor-cell groups were compactly arranged, collagen was decreased in amount. Reticulum fibers sometimes outlined individual cells but more often enclosed groups of cells and were never particularly impressive as to quantity.-this condition was especially evident in one subcutaneous tumor. In this tumor there was, however, somewhat more collagen than was present in the surrounding fat. Where collagen occurred in small patchy areas, associated adult fibroblasts were observed. DISCUSSION The histogenesis of the granular-cell myoblastoma, though not settled, is becoming somewhat clarified. The original concept of origin from adult skeletal muscle or embryonic muscle cells has lost favor in recent years. The finding of cross striations in granular tumor cells has been reported by relatively few authors. There were none observed in our cases, and photomicrographs illustrating such findings in published reports are difficult to interpret. Transition of tumor cells to muscle fibers has been questioned by a number of investigators who point out and illustrate the fact that such apparent transition can occur as a result of tangential sectioning of contiguous tumor and muscle cells. In our one tumor occurring in skeletal muscle (tongue), transitions were not observed, * Sudan IV preparations were studied in 5 eases; no wet tissue was available in Case 6. Before Sudan black B preparations were completed, some wet tissues were lost; hence this method of study was possible on only 9 tumors Cases 2, 4 and 5. In addition to the propylene glycol technic for Sudan black B, frozen sections from a few tumors were stained with this dye dissolved in 70 per cent ethyl alcohol as recommended by the manufacturer. The results were unsatisfactory; the granules of the tumor cells stained a faint gray. FIG. 5 (upper left). Case 5. Marked proliferation of granular cells among the fibers of a small nerve and in the nearly obliterated perineurium. Allochrome. X 350. FIG. 6 (upper right). Case 5. Nerve fiber almost completely replaced by proliferating granular cells. Considerable perineurial fraying. Allochrome. X 350. FIG. 7 (lower left). Case 5. Bizarre epithelial hyperplasia, interpreted as well differentiated squamous-cell carcinoma, surrounded by nests of granular cells. The tip of the rete is seen in the lower right corner. Romanowsky. X 175. FIG. 8 (lower right). Case 5. The lipoid content of isolated clusters of granular cells in the perineurium of a nerve outside the main tumor is shown by a faint sudanophilia as contrasted with the intense blackening of the normal myelin. Sudan black B. X 280.

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7 446 ASHHURN AND RODGER even though strands of tumor cells exhibited a strong tendency to align themselves closely with muscle bundles. Murray 10 in a recent paper on cultural characteristics of three granular-cell myoblastomas concluded that these cultures bore a greater resemblance to cultures of A'arious forms of skeletal muscle, normal and neoplastic, than to cultures of other tissue types to which their origin had been attributed. The storage-cell (histiocyte) concept of origin of these tumors, suggested by Leroux and Delarue, has been favored by a few authors. The suggestion that the stored substance might be glycogen is not supported by study of sections stained by the periodic acid-schiff method, both before and after diastase, digestion. On this point our findings are in agreement with those of Pearse. The study of unstained frozen sections under polarized light revealed no anisotropic substances in the tumor cells. This finding eliminated cholesterol as another possible "storage substance" and at the same time indicates the absence of normal myelin. Pearse concluded that the cell granules contained a large amount of lipoid. While our Sudan black B preparations also were positive, they were never stained deeply as described and illustrated by Pearse. Sudan IV preparations gave faintly positive results. It does not seem that we are justified, from our data, in suggesting a large lipoid content. In any case since a lipoid substance of unknown type and source is present in the cells, it is not possible to rule out "storage tumors" in a consideration of pathogenesis. In 1948 and 1949 Fust and Custer pointed out a previously unobserved close association of nerves and granular cells. Such cells were observed within nerve bundles and in concentric masses, with cores consisting of bundles of axis cylinders and peripheries resembling expanded and frayed nerve sheaths. This, together with the finding of fasciculation in 4 tumors, led them to propose "granular cell neurofibroma" as a new name for these tumors. Pearse in 1950 observed and illustrated similar nerve-tumor cell relationships. In most of our tumors a similar relationship was found. In Fust and Custer's series of 52 tumors, evidence of neurogenesis was observed in 33 (questionable in 4 others). Pearse mentioned finding tumor cells in or within the perineurium in 2 tumors. In our 12 tumors (6 cases), tumor cells were in or within nerve sheaths in 9 (5 cases). This relationship was not always easy to demonstrate but when found was convincing. Occasionally a single involved nerve was found in only one of the sections. In 2 tumors, nerve involvement was easily demonstrated in all sections. In studying these cases we became convinced, with Fust and Custer and Pearse, that the granular cells seen within nerves arose de novo and not by invasion from without. This concept is supported particularly by the definite involvement of nerves, near but outside the tumor area, the presence of granular cells within sheaths without similar cells in the immediately surrounding tissue and the lack of evident histologic and cytologic aggressiveness. The conclusion that tumor cells can and do arise within nerve sheaths is not weakened by the fact that neural association is infrequent in some tumors and not demonstrated in others. In other tumors of various types recognition of foci of origin and transition between tumor and normal cells is often not possible. Our observations do not permit expression of any well-supported opinion as

8 MYOBLASTOMAS 447 to the nature of the precursor cells (Schwann cell or fibroblast). We infer that Fust and Custer lean to the schwann-cell concept, whereas Pearse on both histologic and histochemical grounds would incriminate the fibroblast, both neural and extraneural. Like Pearse and others, we often observed a close relationship between tumor cells and collagen and reticulum fibers. However, we are not inclined to give this finding much weight in the identification of cells, particularly since the granular cells probably are no longer functioning in the same manner as their precursors. We agree with Pearse that one mechanism of tumor growth seems to be by peripheral accretion; a conversion of normal to tumor cells in isolated nests at the tumor margins. We did not recognize such conversion, but the frequent occurrence of isolated small cell nests, without convincing evidence of invasion, gives strong support to this concept. This might be stated differently by suggesting 'multicentric origin. This we believe to be true; based particularly on three of our tumors in which there was no solid cell mass."in these, as stated earlier, tumor cells in small groups were scattered over a relatively wide area separated by abundant, relatively normal, dermal connective tissue. In contrast, the architecture and gross form of some tumors would seem to be better explained by assuming proliferation of the granular cells as a mechanism of growth. For example, one of our subcutaneous tumors was almost spherical. Cells formed compact groups, and collagen and reticulum were present in very small quantities. It must be admitted, however, that mitotic or convincing amitotic division was not observed in granular tumor cells. The finding of mitoses in such cells has been reported infrequently. The extreme epithelial hyperplasia associated with some dermal tumors has been interpreted by some as early squamous-cell carcinoma and by others as pseudoepitheliomatous hyperplasia. Such epithelial change associated with two of our tumors (Case 5) was interpreted originally as early carcinoma, but seems no different from the changes interpreted as pseudoepitheliomatous hyperplasia by some authors. The histologic criteria for definitely separating the two conditions are not sharp. The case reported by Bloom and Ginzler 3 seems to give support to the pseudoepitheliomatous interpretation. Their patient, a 35-yearold woman, had a biopsy of a lip lesion diagnosed "myoblastoma with early squamous carcinoma." There was no further treatment, and the patient was lost to follow-up for 2 years. Examination at this time showed no evident progress of the lip lesion. The occurrence of two or more myoblastomas in the same patient is infrequent, the incidence being approximately 2 per cent. One of Klemperer's 7 patients had 2 lesions of the skin of the lower abdomen. Bloom and Ginzler's patient developed 4 lesions lip, lumbar region, right thigh and right hip. Our patient with 7 tumors of the skin has been described.* The histology and history in these cases wai'rant their acceptance as multiple primary lesions. It seems to us that * Personal communication from Dr. Raymond Bangle, Jr., to the authors: In a scries of cases studied by Dr. Bangle of the National Institutes of Health (report in preparation), one patient had two lesions; one on the tongue, the other involving the fourth toe of the left foot.

9 448 ASHBURN AND RODGER Case 4 of Powell 12 also could well be interpreted as multiple primary lesions. Most of the "numerous firm subcutaneous nodules" had been present as long as the 26-year-old patient could remember; bilateral ovarian and retroperitoneal tumors also were present. These few cases of multiple lesions do not constitute a strong argument for any particular histogenetic theory. However, in this connection one naturally thinks of the tendency of certain tumors of peripheral nerves to be multiple. The occurrence of 6 cases of "myoblastomas" in 1 year in a 400-bed hospital is unusual. However, there seems to be no reason to think that the incidence of these tumors is increasing despite the greater frequency with which they are being reported. SUMMARY Six cases of granular-cell myoblastoma are reported. One patient had 7 lesions. Our histologic observations strongly support the concept of a neural origin for these tumors, first proposed by Fust and Custer. The precursor cell (schwann cell, fibroblast, histiocyte) has not as yet been definitely identified. Acknowledgment is made to Mrs. Verona Wassell for excellent technical assistance. We wish to thank Dr. Raymond Bangle, Jr., of the National Institutes of Health for the allochrome-stained slides 9 used in preparing some of the photomicrographs. REFERENCES 1. ABHIKOSSOFF, A.: Uber Myome ausgehend von der quergestreiften willkiirlichen Muskulatur. Virchows Arch. f. path. Anat., 260: , ABHIKOSSOFF, A.: Weitere Untersuchungen uber Myoblastenmyome. Virchows Arch. f. path. Anat., 280: , BLOOM, D., AND GINZLER, A.: Myoblastoma; report of a case of myoblastoma of the lip followed by multiple tumors of the skin. Arch. Dermat. & Syph., 56: 64S-650, CHIFFELLE, T. L., AND PUTT, F. A.: Propylene and ethylene glycol as solvents for sudan IV and sudan black B. Stain Technol., 26: 51-56, FUST, J. A., AND CUSTER, R. P. Abstract of paper: Granular cell "myoblastomas" and granular cell neurofibromas: separation of neurogenous tumors from the myoblastoma group. Am. J. Path., 24: 674, 194S. 6. FUST, J. A., AND CUSTER, R. P.: On the neurogenesis of so-called granular cell myoblastoma. Am. J. Clin. Path., 19: , KLEMPEREK, P.: Myoblastoma of striated muscle. Am. J. Cancer, 20: , S. LEHOUX, R., AND DELARUE, J.: Sur trois cas de tumeurs a cellules granuleuses de la eavite buccale. Bull. Assoc, frang. p., dtude du cancer, 28: , LILLIE, R. D.: The allochrome procedure: A differential method segregating the connective tissues, collagen, reticulum, and basement membranes into two groups. Am. J. Clin. Path., 21: S, MURRAY, M. R.: Culture characteristics of three granular cell myoblastomas. Cancer, 4: , PEARSE, A. G. E.: The histogenesis of granular cell myoblastoma (? granular cell perineural fibroblastoma). J. Path. & Bact., 62: , POWELL, E. B.: Granular cell myoblastoma. Arch. Path., 42: , 1946.