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CORRESPONDENCE Table of Contents  
Ahead of print publication
Spontaneous regression of hidroacanthoma simplex after skin biopsy

 Department of Dermatology, Shiga University of Medical Science, Setatsukinowa, Otsu, Shiga, Japan

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Date of Submission28-Sep-2020
Date of Decision31-Mar-2021
Date of Acceptance02-Apr-2021
Date of Web Publication19-Jul-2021

How to cite this URL:
Koike T, Kokubu H, Takahashi T, Tanaka T, Fujimoto N. Spontaneous regression of hidroacanthoma simplex after skin biopsy. Dermatol Sin [Epub ahead of print] [cited 2021 Sep 16]. Available from: https://www.dermsinica.org/preprintarticle.asp?id=321876

Dear Editor,

A 50-year-old Japanese woman noticed a nodule on her right knee in 2000. Because it gradually grew, she visited our hospital in 2001. Physical examination showed a reddish, well-demarcated elevated plaque with a diameter of 2 cm on the inner side of her right knee [Figure 1]a. Histological findings of a 3 mm dermal punch biopsy specimen from the plaque revealed hyperkeratosis, acanthosis, well-circumscribed nests of oval basaloid cells within the epidermis with some ductal structures, and slight superficial perivascular infiltration of mononuclear cells [Figure 1]b. We diagnosed her with hidroacanthoma simplex and partially cauterized the base of the tumor with a CO2 laser. She came again due to a recurrence of the tumor in 2007. Physical examination showed a similar plaque at the same site. Histological findings revealed the same observations. Although we decided to treat the tumor with a CO2 laser again, she did not visit our hospital for the treatment of the other half of the tumor. She came again due to an increase of the tumor at the same site in 2015. Physical examination showed multiple reddish papules with a diameter of 1 cm [Figure 1]c. Dermoscopic findings showed whitish reticular structure, round red dots, and loop telangiectasias. Histological findings of a 3 mm dermal punch biopsy specimen revealed similar findings with more mononuclear cell infiltration within the epidermis and around the vessels in the superficial dermis. Immunohistochemical staining showed that the Ki67 positivity rate was 56%, and p53 was positive in the tumor. We diagnosed her with hidroacanthoma simplex again. The tumor spontaneously regressed 16 months after biopsy without any other treatment [Figure 1]d, and no recurrence has been observed for 4 years.
Figure 1: (a) Initial clinical presentation in 2001. (b) Histopathological examination of the plaque revealed well-circumscribed nests of oval basaloid cells within the epidermis with some ductal structures. Hematoxylin-and-eosin staining: original magnification ×40. (c) Clinical presentation in 2015. (d) Clinical presentation at 16 months after biopsy. (e-g) Immunohistochemical staining with CD8 showed that more CD8+ cells around the vessels and within the tumor were observed in 2015 than 2001 and 2007. Original magnification, ×40: tumor in (e) 2015, (f) 2001, and (g) 2007.

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Hidroacanthoma simplex was first described in 1956 as a tumor that originated from the outer cells of the acrosyringium in the intraepidermal epithelioma of Borst Jadassohn.[1] To our knowledge, this is the first case of hidroacanthoma simplex showing spontaneous regression after biopsy. There have been only several types of cutaneous tumors, including benign tumors, such as pseudolymphoma,[2] showing spontaneous regression after biopsy.[3] Moreover, the mechanism of subcutaneous in-transit malignant melanoma showing spontaneous regression after CO2 laser[4] has not been clearly understood thus far. We performed immunohistochemical staining of CD3, CD4, and CD8 for three biopsy samples in this case. Numerous CD8+ cells were observed within the tumor as well as around the vessels in 2015. More CD8+ cells around the vessels and within the rumor were observed in 2015 than 2001 and 2007 [Figure 1]e, [Figure 1]f, [Figure 1]g. We speculated that the treatment with a CO2 laser might have provoked an immune reaction for the tumor and the biopsy procedure enhanced the reaction, which caused spontaneous regression. Merkel cell carcinoma (MCC) is well known,[5] and apoptosis is said to be involved in the regression.[6] Merkel cell polyomavirus (MCPyV) was detected in three of four cases of MCC showing spontaneous regression after biopsy.[5],[7] Thus, we evaluated the virus in this case. However, MCPyV was not detected with polymerase chain reaction using an extract of the paraffin-embedded sample of this case.[7] In this case, MCPyV was not involved in the spontaneous regression after biopsy.


The authors would like to thank Ms. Yuko Tsukamoto for her help in the immunohistochemical analysis.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient has given her consent for her images and other clinical information to be reported in the journal. The patient understands that her name and initials will not be published and due efforts will be made to conceal the identity, but anonymity cannot be guaranteed.

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Conflicts of interest

There are no conflicts of interest.

  References Top

Coburn JG, Smith JL. Hidroacanthoma simplex; an assessment of a selected group of intraepidermal basal cell epitheliomata and of their malignant homologues. Br J Dermatol 1956;68:400-18.  Back to cited text no. 1
Sanchis-Sánchez C, Santos-Alarcón S, Benavente-Villegas FC, Mateu-Puchades A, Soriano-Sarrió MP. Red nodule on the face with “spontaneous” regression. An Bras Dermatol 2017;92:135-7.  Back to cited text no. 2
Toberer F, Mechtersheimer G, Jaschinski H, Enk A, Hakim-Meibodi L, Haenssle HA. Spontaneous Regression of Primary Cutaneous Diffuse Large B-cell Lymphoma, Leg Type. Acta Derm Venereol 2018;98:608-9.  Back to cited text no. 3
Oni G, Monk BM. Spontaneous regression of subcutaneous in-transit malignant melanoma deposits of the lower leg after treatment with the carbon dioxide laser. Clin Exp Dermatol 2009;34:e650-2.  Back to cited text no. 4
Ahmadi Moghaddam P, Cornejo KM, Hutchinson L, Tomaszewicz K, Dresser K, Deng A, et al. Complete spontaneous regression of merkel cell carcinoma after biopsy: A case report and review of the literature. Am J Dermatopathol 2016;38:e154-8.  Back to cited text no. 5
Yagi Y, Fujisawa A, Makiura M, Morita K. Spontaneous regression of Merkel cell carcinoma after biopsy. J Dermatol 2009;36:312-3.  Back to cited text no. 6
Fujimoto N, Nakanishi G, Kabuto M, Nakano T, Eto H, Nakajima H, et al. Merkel cell carcinoma showing regression after biopsy: Evaluation of programmed cell death 1-positive cells. J Dermatol 2015;42:496-9.  Back to cited text no. 7

Correspondence Address:
Hiraku Kokubu,
Department of Dermatology, Shiga University of Medical Science, Setatsukinowa, Otsu, Shiga 520-2192
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/ds.ds_19_21


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