Mycosis fungoides

ICD-O-1 Morphology
Effective 1978 - 1991
ICD-O-2 Morphology
Effective 1992 - 2000
ICD-O-3 Morphology
Effective 2001 and later
for cases diagnosed 1978 and later
Primary Site(s)
C440-C449, C510-C512, C518-C519, C600-C602, C608-C609, C632
Cutaneous (skin) lymphoma which presents with generalized skin lesions. See Module 7.

Not Applicable
Module Rule
Alternate Names
Folliculotropic MF
Granulomatous slack skin
Ketron-Goodman disease
Kiel: small cell, cerebriform
Lukes-Collins: cerebriform T
Pagetoid reticulosis
Woringer-Kolopp type
Mycosis fungoides is a mature T-cell lymphoma presenting in the skin with patches/plaques and characterized by epidermal and dermal infiltration of small to medium-sized T-cells with cerebriform nuclei. So-called "Pautrier microabscesses," consisting of aggregates of cerebriform (highly folded) cells in the epidermis are highly characteristic.

Although patients with mycosis fungoides (MF) typically experience an indolent disease course, a minority undergo a process of large-cell transformation (LCT), which often heralds more aggressive disease and shortened survival. Regrettably, most dermatologists are unfamiliar with LCT, and even fewer understand how to recognize it clinically. Because a diagnosis of LCT typically triggers more aggressive therapy and/or referral to cutaneous T-cell lymphoma (CTCL) centers, it is paramount for clinicians to be able to recognize suspect lesions visually.
Abstractor Notes
Mycosis fungoides (MF) as a rule is limited to the skin with widespread distribution for a protracted period. Extracutaneous disease may occur in advanced stages to lymph nodes, liver, spleen, lungs, and blood.

Characteristics of MF:
1. Indolent clinical course with slow progression over years or sometimes decades.
2. Progresses from patches to more infiltrated plaques and eventually tumors.
3. A combination of patches, plaques, and tumors which show ulceration are common. Rarely, patients present with or develop an erythrodermic stage of disease that lack the hematologic criteria of Sezary syndrome.

There are three variants to MF
1. Folliculotropic MF-characterized by the presence of follicular infiltrates of atypical (cerebriform) CD4+ T lymphocytes often with sparing of the epidermis. Most cases show mucinous degeneration of the hair folicles (follicular mucinosis). Lesions commonly involve the head and neck area, present with grouped follicular papules associated with alopecia. The disease is less accessible to skin-targeted therapies. The disease-specific 5-year survival is approximately 70-80%, which is significantly worse than that of patients with classical plaque stage MF.

2.Pagetoid reticulosis-characterized by the presence of patches or plaques with an intraepidermal proliferator of neoplastic T-cells. The term should only be used for the localized type. The disseminated type would be better classified as Primary cutaneous CD8-positive aggressive epidermotropic cytotoxic TCL (9709/3), or Primary cutaneous gamma-delta TCL (9726/3).

3.Granulomatous slack skin (GSS) - an extremely rare subtype of Cutaneous T-cell lymphoma characterized by the slow development of folds of skin in the major skin folds (axilla, groin) and histologically by a granulomatous infiltrate. Most patients have an indolent clinical course.
Definitive Diagnostic Methods
Genetic testing
Histologic confirmation
Genetics Data
T-cell receptor genes are clonally rearranged
CD4- Pagetoid reticulosis
CD8+ pediatric cases
TCRa beta +
Other RX
Transformations to
There are no known transformations
Transformations from
There are no known transformations
Corresponding ICD-9 Codes
202.1 Mycosis fungoides
Corresponding ICD-10 Codes
C84.0 Mycosis fungoides
Corresponding ICD-10-CM Codes (U.S. only)
C84.0 Mycosis fungoides (effective October 01, 2015)
Signs and Symptoms
Itchy, painful, peeling and reddened skin
Skin lesions: papules, patches, plaques or tumors
Ulcerated skin lesions, which may become infected
Progression and Transformation
Epidemiology and Mortality
Age: mostly elderly, although can occur in children and adolescents
Survival: patients with limited disease have excellent prognosis; those with extensive disease have a poor prognosis