Histiocyte‐rich pleomorphic mastocytoma: an uncommon variant mimicking juvenile xanthogranuloma and Langerhans cell histiocytosis

Abstract

An 11-year old Caucasian female with a remote history of urticaria pigmentosa presented with a neck mass. A biopsy demonstrated a large intradermal nodule composed of unusually large epithelioid mast cells, including a prominent subset with bi-lobed and multi-lobed nuclei. By immunohistochemistry, the cells expressed CD117 (C-Kit), mast cell tryptase, CD68, and CD25, and were negative for CD163, CD1a, and S-100, confirming the diagnosis of mastocytoma. Equally prominent was an admixed infiltrate of CD68 and CD163-positive xanthomatous histiocytes that included Touton-type giant cells. Eosinophils were abundant. At 7 months follow-up, there was no recurrence of the lesion following complete excision. However, given the unusual cytologic features, close clinical observation is warranted, as the long-term biologic potential of mastocytoma with this degree of cytologic atypia is uncertain. Awareness of this unusual morphologic variant is also important as the histologic features may mimic such childhood neoplasms as juvenile xanthogranuloma and Langerhans cell histiocytosis.

CD1a-positive familial cutaneous mastocytosis without germ-line or somatic mutations in c-kit

“…A few MCs with eosinophilic granules were also presented in the same region, and the number of these pleomorphic MCs decreased gradually towards the lower dermis. Previously, pleomorphic MCs corresponding to those seen in the present study were investigated in paediatric cutaneous mastocytosis of nodular infiltration‐type on the scalp and the neck . The latter case is the same one reported with xanthomatous histiocytes, and had presented with scalp pruritis .…”

“…Previously, pleomorphic MCs corresponding to those seen in the present study were investigated in paediatric cutaneous mastocytosis of nodular infiltration‐type on the scalp and the neck . The latter case is the same one reported with xanthomatous histiocytes, and had presented with scalp pruritis . Pleomorphic MCs are haematologically classified as atypical MCs type II (promastocytes) .…”

“…In this case, spindle MCs infiltrated interstitially into the upper dermis accompanied by less frequent S‐100 + CD1a + histiocytes . The other case was an 11‐year‐old girl with brown macules and a nodule infiltrated predominantly by MCs in the presence of xanthomatous histiocytes . In contrast, a MC‐rich variant of histiocyosis X was reported as self‐healing histiocytosis, or urticating Hashimoto–Pritzker disease .…”

Mast cell sarcoma: a rare and potentially under-recognized diagnostic entity with specific therapeutic implications

“…This hypothesis is supported by the fact that the exon 8 KIT mutation seen in case 2 is more characteristic of pediatric cutaneous mastocytosis than adult systemic mastocytosis. 19 There are at least two prior reports of cutaneous mastocytomas with atypical cytological features, 20,21 including occasional neoplastic mast cells with bilobed nuclei, but the cases of cutaneous mast cell sarcoma differed from these in showing frankly malignant cytomorphology, with a high degree of tumor cell anaplasia, numerous mitoses (including atypical forms), and a relatively high Ki-67 index.…”

Pediatric Mast Cell Sarcoma of Temporal Bone With Novel L799F (2395 C>T) KIT Mutation, Mimicking Histiocytic Neoplasm

“…9 In fact, because of its rarity and unusual histology, MCS may initially be confused with other types of sarcoma, such as myeloid sarcoma (MS), myelomastocytic leukemia (MML), or, especially, histiocytic neoplasms including Langerhans cell histiocytosis (LCH) and histiocytic sarcoma. 10 Mast cell neoplasms frequently show KIT mutation. In particular, the D816V mutation is often seen in systemic mastocytosis (SM).…”