Proposal for a pathogenesis-based classification of tumoral calcinosis

Deposition of calcium in skin is currently categorized into a group of disorders referred to as calcinosis cutis. Divisions between types and subtypes within this confusing classification are predominantly based on morphologic differences in the calcification and serve to obscure pathogenesis. This is especially evident in a subtype of calcinosis cutis, known as tumoral calcinosis. Calcifications in cases of tumoral calcinosis share the following characteristics, but without evidence of a common pathogenesis: large size, juxtaarticular location, progressive enlargement over time, a tendency to recur after surgical removal, and an ability to encase adjacent normal structures. The goal of this study was to formulate a pathogenesis-based classification for cases of tumoral calcinosis.

In a literature review 121 cases of tumoral calcinosis were identified. These cases, along with a case evaluated in our clinic, were reviewed retrospectively, and their features compared.

Analysis suggests three pathogenetically distinct subtypes of tumoral calcinosis: (1) Primary normophosphatemic tumoral calcinosis: patients have normal serum phosphate, normal serum calcium, and no evidence of disorders previously associated with soft tissue calcification; (2) primary hyperphosphatemic tumoral calcinosis: patents have elevated serum phosphate, normal serum calcium, and no evidence of disorders previously associated with soft tissue calcification; and (3) secondary tumoral calcinosis: patients have a concurrent disease capable of causing soft tissue calcification. Justification for this classification is based on the presence or absence of disorders known to promote soft tissue calcification and statistically significant differences in family history, mean calcification number, mean serum phosphate level, and calcification recurrence after excision.

A classification for tumoral calcinosis is devised that outlines potential pathogenetic mechanisms and predicts response to therapy and prognosis. Analysis of other forms of calcinosis cutis may reveal definable pathogenetic differences that suggest a coherent classification for all cutaneous calcinoses.