Clear cell acanthoma

This is a nice example of a clear cell acanthoma from the upper thigh of a middle-aged woman. Most of these uncommon lesions we see come from some part of the lower extremity, although certainly not restricted to this site. There are some psoriasiform changes of the epidermis, with few neutrophils in the parakeratotic scale, thinning of the suprapapillary plates, and epidermal hyperplasia.  Some reports demonstrate dermatoscopic similarities of clear cell acanthoma and psoriasis. I can see how this flat lesion could look like a psoriatic plaque clinically, while some lesions are more papillated and acanthotic. You can usually see prominent clear cell change on H&E, however, the PAS-stain also really highlights the prominent glycogen in the cytoplasm, highlighting the epidermis that lacks phosphorlyase and thus cannot break down glycogen. Dr. Mihm and his colleague Dr. Caplan have posted a nice review of a case showing a lesion that is more papillated, showing the variability of these lesions.


J Eur Acad Dermatol Venereol. 2003 Jul;17(4):452-5. Psoriasis-like dermoscopic pattern of clear cell acanthoma. Bugatti L, Filosa G, Broganelli P, Tomasini C.
Dermatology. 2001;203(1):50-2. The dermatoscopic pattern of clear-cell acanthoma resembles psoriasis vulgaris. Blum A, Metzler G, Bauer J, Rassner G, Garbe C.


Merkel Cell Carcinoma with Intraepidermal or In Situ Component

Aside from those scary nevoid melanomas or finding a small focus of melanoma arising in a nevus, one other killer tumor to be on the look out for is the Merkel Cell Carcinoma or primary neuroendocrine carcinoma of skin. I’ve looked at some of these tumors at scanning magnification that have looked very much like a basal cell carcinoma, especially in a partially sampled or fragmented lesion, but usually there is some trigger that catches the eye and helps you not miss this diagnosis. Thank your lucky stars for these triggers. One such trigger is found in this biopsy that was sent to us as a basal cell carcinoma clinically.  This trigger at low power is the intraepidermal or in situ component, with pagetoid spread of the hyperchromatic cells within the epidermis.  This is definitely not a characteristic of a basal cell carcinoma.  The cell stain nicely with CK20 in the paranuclear dot-like pattern.  There is also staining with synaptophysin, but very little staining with chromogranin.  The S100 was negative, which I would also recommend performing on these tumors to help rule out melanoma with neuroendocrine differentiation.  The cytology of the cells in this tumor is much different from a basal cell carcinoma, demonstrating finely stippled chromatin and the tumor nests in the dermis do not show peripheral palisading or retraction from the dermis with mucinous stroma.  With a good review of this lesion, it is not hard to make the diagnosis.  It’s just one of those malignant tumors that keeps you from going too fast.

J Cutan Pathol. 2010 Oct;37(10):1112-3. Merkel cell carcinoma in situ associated with actinic keratosis: fortuitous or serendipitous? Ferrara G, Goos SD, Stefanato CM.

Am J Dermatopathol. 2004 Jun;26(3):230-3. A case of intraepidermal Merkel cell carcinoma within squamous cell carcinoma in-situ: Merkel cell carcinoma in-situ? Al-Ahmadie HA, Mutasim DF, Mutema GK. Department of Pathology and Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, OH, USA.

Hailey-Hailey Disease

The last 7 months have been pretty busy as I’ve been working on a new laboratory here in Knoxville and now I’m finally getting a bit of time where I can hopefully start posting regularly again. We received a really good case of Hailey-Hailey disease the other day that demonstrated the classic dilapidated brick wall appearance. This biopsy was from the axilla of a middle aged woman, which is a classic location. Still trying to get my camera settings right. I am using an Infinity2 Lumenara camera paired with an Olympus microscope and LED light source. I receive no royalties for endorsing this microscope, but I really like the LED light source, it’s easy on the eyes. Not sure if it reflects well in the photos, but I end up manipulating the brightness & contrast anyway so it probably doesn’t make a difference.

CD30-positive Lymphoproliferative Disorder/ Lymphomatoid Papulosis

This biopsy came from a patient in their 50s with multiple recurrent lesions on the lower extremities that would ulcerate and then regress.  The clinical suspicion was for pityriasis lichenoides versus folliculitis.  The epidermis is necrotic and there is a mixed infiltrate in the superficial dermis.  I didn’t see viral cytopathic change, arthropod remants or folliculitis.  I was concerned about a population of large atypical appearing lymphocytes in the superficial dermis and the immunohistochemistry studies showed that this population of cells stained with CD30 with a background of smaller CD3 positive T-cells.  Given the clinical presentation and histologic findings, this fit well for lymphomatoid papulosis.  In cases like this, my diagnosis is usually “CD30-positive lymphoproliferative disorder”, with a comment describing the lesion and recommendation for follow-up evaluation since there is a higher risk for development of hematologic malignancy in patients with lymphomatoid papulosis.  Determining how many CD30 positive cells is too many can be a challenge.  There are plenty of cautionary reports in the medical literature that show increased CD30-positive cells in conditions such as viral infections, drug reactions, arthropod assaults, and pityriasis lichenoides, among others.  Most authors stress careful clinical pathological correlation when making this diagnosis.  There is a nice free full text article in Blood from Oct. 2011 from the Cutaneous Lymphoma Task Force of the European Organization for Research and Treatment of Cancer, the International Society for Cutaneous Lymphomas, and the United States Cutaneous Lymphoma Consortium, with therapeutic recommendations for CD30-positive lymphoproliferative disorders.


  1. EORTC, ISCL, and USCLC consensus recommendations for the treatment of primary cutaneous CD30-positive lymphoproliferative disorders: lymphomatoid papulosis and primary cutaneous anaplastic large-cell lymphoma.  Blood. 2011 Oct 13;118(15):4024-35. Epub 2011 Aug 12.  Kempf W et al. 
  2. In search of prognostic indicators for lymphomatoid papulosis: A retrospective study of 123 patients. J Am Acad Dermatol. 2011 Oct 7. de Souza A, El-Azhary RA, Camilleri MJ, Wada DA, Appert DL, Gibson LE.
  3. CD30+ lymphoproliferative disorders: histopathology, differential diagnosis, new variants, and simulators.  J Cutan Pathol. 2006 Feb;33 Suppl 1:58-70.  Kempf W.

Post Herpes Zoster Granulomatous Dermatitis with Vasculitis

Without any clinical information, I hesitate to make this diagnosis.  The dermatologist said this elderly patient presented with a cluster of erythematous slighlty indurated lesions in a unilateral dermatomal distribution on the right flank.  He said if there were vesicles, it would be perfect for herpes zoster/shingles.  The patient was otherwise healthy. This biopsy had a superficial and mid-dermal granulomatous infiltrate, with multinucleate histiocytes and lymphocytes predominating.  Some areas looked granuloma annulare-like, although without increased mucin.  Special stains were negative for fungal and acid fast organisms and I did not identify herpes viral cytopathic changes.  Focusing on the dermal changes, I almost brushed past the vasculitis in the subcutis, which appears primarily lymphocytic.  I did not see any vasculitis in the dermis.   Carlson noted one case of lymphocytic vasculitis in a post-herpes infection case, but typically the vasculitis is more often reported to be granulomatous in post-herpes zoster infection. The vessel went away on deeper levels so I couldn’t evaluate it further.  I think it’s important to rule out other possible causes of vasculitis and other sources of infection, but I think given the clinical presentation and the histology, this was a nice case of post herpes zoster granulomatous dermatitis with vasculitis.

Cutaneous Vasculitis Update: Neutrophilic Muscular Vessel and Eosinophilic, Granulomatous, and Lymphocytic Vasculitis Syndromes J. Andrew Carlson and Ko-Ron Chen, MD, PhD. Am J Dermatopathol 2007;29:32–43

Squamous Cell Carcinoma with Monster Cells

Considering all the Monster cells, the Giant cells, the Natural Killer cells, and the Ghost cells, histopathology is scary business.  Of course I cannot identify the Natural Killer cells on H&E stained sections, I include them in my list because they sound so fierce.  If you can identify them without immunohistochemistry, you have superNatural sKills.  This biopsy shows a squamous cell carcinoma and the marked atypia and pleomorphism of the ‘monster” cells is quite interesting.  More than the usual degree of atypia anyway.  I included more high magnification shots so you can get up close with these monstrosities.  

 I admit, I missed the timing on this post and should have saved it for Halloween.


Basaloid squamous cell carcinoma with ‘monster’ cells: a mimic of pleomorphic basal cell carcinoma. Defty CL, Segen J, Carter JJ, Ahmed I, Carr RA. J Cutan Pathol. 2011 Apr;38(4):354-6.

Chondroid syringoma (mixed tumor of skin) with hair matrix differentiation

This lesion caught my eye because at the edge it looks like a pilomatrixoma, with ghost cells and prominent foreign body giant cell response. The bulk of the lesion is a typical mixed tumor or chondroid syringoma.  A few cells along the ducts showed some sebaceous differentiation as well. These mixed tumors are appropriately named, as they present with a mixed bag of tricks.  It might lead to misdiagnosis in a small sample. These findings are reported in current textbooks, but a nice reference on this goes back to 1984 with an article by Dr. Ron Rapini.  His case was better because it showed some basaloid cells with transition to the ghost cells.  I noticed at the bottom of his paper it was sponsored by a grant from the Dermatology Foundation. This demonstrates the value of joining this foundation, as the foundation has supported some outstanding people early in their career.


Hair matrix differentiation in chondroid syringoma. Rapini RP, Kennedy LJ, Golitz LE. J Cutan Pathol. 1984 Aug;11(4):318-21.

Cutaneous mixed tumor containing ossification, hair matrix, and sebaceous ductal differentiation.  Akasaka T, Onodera H, Matsuta M.  J Dermatol. 1997 Feb;24(2):125-31.