Solitary pink papule in an elderly man.

A 72-year-old, healthy man presented with an asymptomatic, stable, solitary, 5-mm × 5-mm, pink, dome-shaped papule on his neck that had been present for at least 6 months (Fig 1). There were no identifiable triggers, including exposure to drugs, radiation, or trauma to that area. A physical examination was unremarkable and did not demonstrate lymphadenopathy or hepatosplenomegaly. Polarized dermoscopy demonstrated a homogeneous, pink papule with serpentine, dotted, and short linear vessels; white, shiny lines; and white rosette structures (Fig 2). Pathology showed a heavy infiltrate of intermediate-to-large, atypical lymphoid cells involving the papillary dermis, dermoepidermal junction, and epidermis. The atypical lymphoid cells monotonously stained for CD3, diffusely expressed CD30 and nuclear MUM1 (bright), and were double-negative for CD4 and CD8 (Figs 3 and 4). ALK-1, SOX10, PD1, and CD138 were negative. No further investigations were undertaken.

Fig 1

Fig 2

Fig 3

Fig 4

Question 1: Given the history and images, what is the most likely diagnosis?

Primary cutaneous anaplastic large cell lymphoma with 6p25.3 rearrangement

Transformed CD30+ mycosis fungoides (MF)

Lymphomatoid papulosis (LyP) with 6p25.3 rearrangement (LyP 6p25.3)

LyP type C

LyP type B

Answers:

Primary cutaneous anaplastic large cell lymphoma with 6p25.3 rearrangement – Incorrect. Histologically, this entity can also present with a nodular dermal infiltrate of CD30+, atypical lymphoid cells but no evidence of epidermal involvement of CD30+ cells, which is one of characteristic features of this subtype of LyP., The 6p25.3 rearrangement on the DUSP22 locus has been correlated with the inhibition of tumor suppression.

Transformed CD30+ MF – Incorrect. This patient had no prior diagnosis of MF, and MF does not usually present with one solitary papule on the head and neck region.

LyP 6p25.3 – Correct. This entity was first reported by Karai et al in 2013. It usually presents in men, at a mean age of 75, as one or a few papulonodules at a single site. Pathology reveals a dermal nodule composed of lymphocytes with overlying CD30+, MUM1+, atypical lymphocytes in the epidermis, resembling pagetoid reticulosis., In general, surveillance is recommended for patients with LyP given the risk for developing secondary lymphomas; however, Karai et al did not note the development of lymphomas in any of their patients.

LyP type C – Incorrect. LyP type C shares certain histologic features of LyP with 6p25.3 rearrangement, such as nodular infiltrates in lymphocytes; however, CD4 and TIA1 are usually also expressed., The epidermal involvement of CD30+ lymphoid cells is not a characteristic feature of LyP type C. Clinically, it presents at a mean age of 38 and is typically characterized by disseminated papulonodules.,

LyP type B – Incorrect. The epidermal findings of LyP 6p25.3 are similar to those of LyP type B; however, LyP type B expresses CD4 and has more of a band-like dermal lymphocytic infiltrate with no evidence of the epidermal involvement of CD30+ lymphoid cells.,,

Question 2: What is the common immunohistochemical staining pattern found in LyP with a 6p25.3 rearrangement?

CD3+, CD30+, MUM1+, ALK−, CD4, and CD8 are often (but not always) negative

CD30+, CD4+, ALK−, EMA−, CLA+

CD4+, CD8−, CD30+/−

CD4+, CD8−, CD30+

CD4+ greater than CD8+, CD30+/−, CD3−, CD7−

Answers:

CD3+, CD30+, MUM1+, ALK−, CD4, and CD8 are often (but not always) negative – Correct. A review of 11 patients with LyP 6p25.3 showed this pattern most often. Of note, the CD30 stain is more prominent in the dermis than in the epidermis in most reported cases; this was seen in our patient as well (Fig 4).,

CD30+, CD4+, ALK−, EMA−, CLA+ – Incorrect. This is the staining pattern for primary cutaneous anaplastic large cell lymphoma.

CD4+, CD8−, CD30+/− – Incorrect. This is the staining pattern for LyP type B.

CD4+, CD8−, CD30+ – Incorrect. This is the staining pattern for LyP type C.

CD4+ greater than CD8+, CD30+/−, CD3−, CD7− – Incorrect. This is the staining pattern for transformed MF.

Question 3: Which of the following is a dermoscopic pattern for LyP 6p25.3?

A white, structureless area surrounding tortuous vessels that extends centrifugally

A central, white, structureless area with vessels present on the periphery

Vessels surrounding an area of necrosis and ulceration

A brown-gray, structureless area with no vessels

Linear, curved, and tortuous vessels; rosettes; and shiny, white lines

Answers:

A white, structureless area surrounding tortuous vessels that extends centrifugally – Incorrect. This pattern is seen in the initial stage of more common forms of LyP.,

A central, white, structureless area with vessels present on the periphery – Incorrect. This pattern is seen with more mature lesions of more common forms of LyP.,

Vessels surrounding an area of necrosis and ulceration – Incorrect. This pattern is seen in more common forms of LyP prior to the cicatricial phase.,

A brown-gray, structureless area with no vessels – Incorrect. This pattern is seen with scarring or postinflammatory dyspigmentation in more common forms of LyP.,

Linear, curved, and tortuous vessels; rosettes; and shiny, white lines – Correct. To our knowledge, this pattern has not yet been described, and it was seen in our patient with LyP with 6p25.3 gene rearrangement.

Conflicts of interest

None disclosed.