Myxoid variant of anaplastic large cell lymphoma involving the skin: a case report.

We report the case of a 62-year-old white male who presented with a 2.6-cm ulcerating mass on the skin of the left buttock and ipsilateral inguinal lymphadenopathy. Microscopic sections of the skin lesion showed a nodular and plaque-like growth pattern of a mixed cellular infiltrate throughout the dermis and subcutaneous tissue with prominent myxoid change. There was a dominant population of medium-sized mitotically active atypical cells that expressed CD30, CD4 and EMA. These atypical cells were mixed with eosinophils, neutrophils, mature lymphocytes and histiocytes. Tissue from the inguinal lymphadenopathy showed similar pathologic features, although no residual lymph node tissue was present. A diagnosis of secondary anaplastic large cell lymphoma, myxoid variant, with skin and lymph node/perinodal soft tissue involvement was rendered at the time of complete excision of the buttock mass. The patient received five cycles of CHOP (cyclophosphamide, doxorubicin, vincristine and prednisone) chemotherapy with complete resolution of lymphadenopathy and no residual cutaneous disease. He was disease-free by PET/CT scan and physical examination at 16 months after chemotherapy. We present this case to highlight the histopathologic and immunophenotypic features of this entity with a discussion of the differential diagnosis and a review of the literature.

Suppurative inflammation with microabscess and pseudocyst formation is a characteristic histologic manifestation of cutaneous infections with rapid-growing Mycobacterium species.

Mycobacterial infections of the skin classically cause a granulomatous tissue reaction. We have observed a suppurative pattern of inflammation associated with infections by rapid-growing Mycobacterium species in immunocompromised patients. We report 6 cases in skin and soft tissue with an unusual but consistent lack of a predominance of granulomatous inflammation. Of the 6 cases, 4 had predominantly (approximately 75%) suppurative inflammation, 1 case predominantly demonstrated (approximately 75%) a mix of acute and chronic inflammation, and 1 case showed an approximately equal contribution of suppurative and granulomatous inflammation. All 6 cases showed abscess formation and numerous acid-fast bacilli (AFB) on AFB stain and were confirmed by tissue culture. Of these 6 cases, 2 had microabscesses with central pseudocysts harboring microorganisms. Five patients were taking oral prednisone, and 1 had an uncharacterized immunodeficiency. These cases highlight the need for awareness of this unusual manifestation of infection with rapid-growing Mycobacterium species, particularly in immunocompromised patients.