Psammomatous Melanotic Schwannoma: A Challenging Histological Diagnosis

Abstract

Psammomatous melanotic schwannoma (PMS) is a rare pigmented tumor that can be part of the Carney complex. Here, we describe the case of a 35-year-old female patient presenting an isolated subcutaneous PMS. Histopathological analysis could not formally exclude the malignant nature of the tumor. The challenging histological diagnosis and consequently the management of the patient are described.

Intracranial Melanotic Schwannomas: Rare and Distinctive Tumors to Know Due to their Risk of Recurrence and Metastases

“…Thus, the lack of psammomatous bodies does not exclude Carney complex. Recently, the inactivating mutation of the tumor-suppressor gene PRKAR1A was found in about 50% of Carney complex cases [34]. In our case, no psammomatous bodies were found, and there was no other endocrine, cutaneous, or conjunctive detected abnormality, or family history.…”

Pathology of Melanotic Schwannoma

“…Microscopically, MSs are circumscribed but not encapsulated (Figure 1, A) and contain plump spindle and epithelioid cells arranged in interlacing fascicles or nests (Figure 1, B). [1][2][3][4][5][6][7][8][9][10][11]15,17 The tumors are characterized by accumulation of melanin in neoplastic cells and associated melanophages (Figure 1, C). Cytoplasmic pigmentation varies greatly.…”

“…Melanotic schwannomas associated with CC show sheets of adiposelike cells and psammoma bodies. [1][2][3][4][5][6][7][8][9][10][11] Psammoma bodies may be focal and only identifiable after extensive search (Figure 2, A). MS usually lacks Verocay bodies, microcysts, a well-formed capsule, and thick-walled hyalinized blood vessels.…”

“…11,15 Immunohistochemical staining for S100, SOX10, HMB-45, Melan-A, p16, and vimentin produces positive results ( Figure 3, A through D). [1][2][3][4][5][6][7][8][9][10][11] Linear, pericellular immunoreactions of both laminin and collagen IV are detected in all cases of MS. 5 Ultrastructurally, numerous elongated tumor cell processes, duplicated basement membrane, and melanosomes are observed in all developmental stages. 16,17,31…”

Adrenal Microcystic Reticular Schwannoma

“…They affect all ages and occur prominently in the head and neck as well as in flexor surfaces of upper and lower extremities (1,2). Ninety percent are sporadic, however, they can occur as part of schwannoma syndromes, like schwannomatosis and neurofibromatosis type 2 (3,4), or as part of Carney complex (5,6).…”