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


This neoplasm is not reportable

Primary Site(s)

See Abstractor Notes

Abstractor Notes

This is not a reportable histology.

Alternate Names

Diffuse cutaneous mastocytosis
Extracutaneous mastocytoma
Juvenile cutaneous mastocytosis
Maculopapular cutaneous mastocytosis (MPCM)
Mast cell tumor, NOS
Mastocytoma, NOS
Mastocytoma of skin
Solitary mastocytoma of skin


The diagnosis of cutaneous mastocytosis (CM) requires the demonstration of typical clinical findings and histological proof of abnormal mast cell infiltration of the determine.

In cutaneous mastocytosis, there is no evidence of systemic involvement in the bone marrow or any other organ. In addition, the diagnostic criteria for systemic mastocytosis is not fulfilled; however, patients with cutaneous mastocytosis may present with one or two of the minor diagnostic criteria for systemic mastocytosis, such as an elevated serum tryptase level or abnormal morphology of mast cells in the bone marrow.

Three major variants of cutaneous mastocytosis are recognized:

1. Urticaria pigmentosa/maculopapular cutaneous mastocytosis: 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.

2. 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.

3. 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


Radiation therapy

Corresponding ICD-9 Codes

238.5 Neoplasm of uncertain behavior of 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)

D47.01 Cutaneous mastocytosis (effective October 01, 2015)
D47.09 Other mast cell neoplasms of uncertain behavior (effective October 01, 2015)


Swerdlow SH, Campo E, Harris NL, Jaffe ES, Pileri SA, Stein H, Thiele J (Eds):
WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues (Revised 4th edition)
IARC: Lyon 2017
Section: Mastocytosis
Pages: 65-68

International Classification of Diseases for Oncology, Third Edition, Second Revision. Geneva: World Health Organization, 2020.
Section: ICD-O-3.2 (2020) Morphological Codes