This neoplasm is not reportable.


Cutaneous mastocytosis

ICD-O-1 Morphology

9740/1: Mastocytoma
Effective 1978 - 1991

ICD-O-2 Morphology

9740/1: Mastocytoma
Effective 1992 - 2000

ICD-O-3 Morphology

9740/1: Mastocytoma
Effective 2001 and later

Not Reportable

This neoplasm is not reportable

Primary Site(s)

See Abstractor Notes

Alternate Names

Diffuse cutaneous mastocytosis
Juvenile cutaneous mastocytosis
Extracutaneous mastocytoma
Mastocytoma, NOS
Mastocytoma of skin
Solitary mastocytoma of skin
Urticaria pigmentosa (UP)/maculopapular cutaneous mastocytosis (MPCM)


Mastocytosis is due to a clonal, neoplastic proliferation of mast cells that accumulate in one or more organ systems. It is characterized by the presence of multifocal compact clusters or cohesive aggregates/infiltrates of abnormal mast cells. Subtypes of mastocytosis are recognized mainly by the distribution of the disease and clinical manifestations.

Types of mastocytosis coded to 9740/1 are non-reportable: cutaneous mastocytosis (CM) where the mast cell infiltration is confined to the skin; and extracutaneous mastocytoma , an extremely rare unifocal low-grade mast cell tumor with no skin lesions.

Abstractor Notes

The diagnosis of cutaneous mastocytosis (CM) requires the demonstration of typical clinical findings and histological proof of abnormal mast cell infiltration of the dermis. In cases of isolated CM, there is no evidence of systemic involvement using such parameters as elevated levels of total serum typase or organomegaly. Recently, criteria for the diagnosis of CM have been further refined and three major variants of CM are now recognized: Urticaria pigmentosa (UP)/maculopapular cutaneous mastocytosis (MPCM), diffuse cutaneous mastocytosis, and solitary mastocytoma of skin.

Urticaria pigmentosa/maculopapular cutaneous mastocytosis is the most frequent form of CM. In children the lesions of UP tend to be larger and papular. Histopathology typically reveals aggregates of spindle-shaped mast cells filling the papillary dermis and extending as sheets and aggregates into the reticular dermis, often in perivascular and periadnexal positions. A subvariant, usually occurring in young children, presents as non-pigmented, plaque-forming lesions. In adults the lesions are disseminated and tend to be red or brown and macular or maculopapular.

Diffuse cutaneous mastocytosis occurs almost exclusively in childhood. The skin is diffusely thickened and may have an orange peel appearance. There are no individual lesions. Atypical cells are not present, which can help distinguish this disease from a mast cell sarcoma (9740/3) occurring in the skin.

Mastocytoma of skin occurs as a single lesion, almost exclusively in infants. These mast cell infiltrates may extend into the subcutaneous tissues.

Extracutaneous mastocytomas has been reported in the lung. This isolated mast cell tumor has a non-destructive growth pattern.

Definitive Diagnostic Methods

This data item does not apply



Corresponding ICD-9 Codes

238.5 Histiocytic and mast cells

Corresponding ICD-10 Codes

D47.0 Histiocytic and mast cell tumors of uncertain and unknown behavior

Corresponding ICD-10-CM Codes (U.S. only)

D47.0 Histiocytic and mast cell tumors of uncertain behavior (effective October 01, 2015)