Symplastic glomus tumor – a rare but distinct benign histological variant with analogy to other ‘ancient’ benign skin neoplasms

Abstract

A 78-year-old woman presented with a nail deformity of the index finger of the left hand associated with paroxysmal pain upon cold exposure. Histologically, a well-circumscribed tumor of 3 mm diameter was found in the dermis. The neoplastic cells in some areas were of pronouncedly variable size and cytomorphology, mostly epithelioid in shape, with eosinophilic cytoplasm and indistinctly defined cell borders. Pronounced nuclear pleomorphism and atypia were striking features, but no mitotic figures were noted. Multinuclear cells were present as were numerous small-to-medium vessels throughout the tumor. The tumor stroma showed myxoid areas. Immunohistochemistry showed cytoplasmic and membranous expression of smooth muscle actin and vimentin. The histological features and immunoprofile were consistent with the diagnosis of symplastic glomus tumor, a rare histological variant, which has been defined as a glomus tumor exhibiting marked nuclear atypia, in the absence of any other criteria for malignancy. The biological behavior of the tumor is benign. It is essential to differentiate this entity from malignant glomus tumor, which has metastatic potential. Even prominent cellular atypia and nuclear pleomorphism in a glomus tumor as in our case is not a marker of malignancy in the absence of additional criteria.

Symplastic glomus tumor

“…Clinical and pathological assessment of 52 previously diagnosed atypical or malignant glomus tumors showed that high nuclear grade alone was not associated with an increased metastatic risk 1 . This type of glomus tumor is classified as a symplastic glomus tumor and 14 cases have been reported to date 1–6 . A comparison with cases of classical and symplastic glomus tumors reported previously showed that our case shared several factors with the typical clinical picture, including age of onset, female predominance, size and depth of the tumor, and digital distribution.…”

Intradermal nevi with atypical nuclei in the elderly: The senescent nevus

“…The adjective ''symplastic'' has been applied to other cutaneous tumors including trichodiscoma, leiomyoma, glomus tumor, and hemangioma. 4,[12][13][14] However, as previously noted, the definition of ''symplast'' is inappropriate. 4 The ''ancient'' nevus was described in 1993.…”

Acral manifestations of soft tissue tumors

“…46 Symplastic change has been described in several cases of glomus tumor and must not be overinterpreted as a malignant feature. 47,48 The principal differential at scanning magnification may include adnexal tumors, but further examination unveils the characteristic appearance of the glomus family of tumors. Simple excision is the mainstay of treatment.…”