GRANULAR-CELL CHANGE IN SMOOTH-MUSCLE TUMORS OF SKIN AND SOFT-TISSUE

Nine smooth muscle tumours, arising at a variety of sites and showing granular cell change of their cytoplasm, have been studied morphologic ally and immunohistochemically. The age of the patients ranged from 6 to 78 years (median 42 years); seven patients were female. Two rumours each arose in the dermis or subcutaneous tissue while the other five cases were situated in deeper soft tissue. Three of the lesions arose in the lower limbs, two in the pelvis and one each in the regions of t he elbow, shoulder, breast and buttock. Follow-up in eight patients wa s available and revealed local recurrence in three and pulmonary metas tases in two cases. All cases showed at least focally the light micros copic features of a smooth muscle tumour and demonstrated moderate to strong positivity for a-smooth muscle actin. Five were also HHF-35 pos itive and three were desmin positive. Noteworthy was strong positivity for the 'melanoma associated' antigen NKI/C3 in all cases. Six cases stained also weakly positive for NSE, but all were S-100 protein negat ive. The former is not specific but is the most reliable marker of les ions showing granular cell change. Granular cytoplasmic change represe nts simply a cytological phenotype, apparently representing a characte ristic metabolic alteration, not exclusively associated with Schwann c ell rumours. Tumours containing granular cells are best classified acc ording to their line of specific cellular differentiation if possible.