myeloid leukemia cutis ( lc ) may be the presenting sign in patients with myeloid disorders , like acute myelogenous leukemia ( aml ) . it occurs in approximately 13% of patients with aml and classically presents later in the disease , when neoplastic leukocytes of myeloid lineage infiltrate the epidermis , dermis , or subcutis . in some cases , however , the appearance of lc is the first evidence of leukemia and the atypical myeloid forms can be identified in the infiltrate underlying an unrelated skin lesion . the clinical appearance of the skin lesions is fairly non - specific and as in this case , the clinical appearance may reflect only the superficial cutaneous neoplasm , rather than the underlying leukemia . a high index of suspicion is required as correct interpretation of the biopsy leads to the correct diagnosis and allows early intervention . in our patient , the biopsy was performed for confirming a keratotic lesion ; but the underlying leukemia proved to be the more important diagnosis . an 85-year - old - female patient presented with skin lesions on her right temple and left nasal sidewall , suspicious for squamous cell carcinoma ( scc ) . the lesion on right temple demonstrated an actinic keratosis ( ak ) with an underlying dermal infiltrate of immature myeloid cells [ figures 1 and 2 ] . immunohistochemical staining for myeloperoxidase [ figure 3 ] , cd68 and cd34 supported a diagnosis of myelogenous leukemia . hematoxylin - eosin stained sections , 400 myeloperoxidase stain in cells of myeloid lineage , 200 aml may present as an isolated papule or nodule , but the manifestations may be as diverse as an erythematous , pruritic , morbilliform eruption or patches and plaques mimicking mycosis fungoides . a diagnosis of lc in the presence of aml is a poor prognostic indicator and strongly correlates with additional sites of extramedullary involvement . this can alter the appropriate treatment regimen for a patient , making the diagnosis of particular importance . the cells commonly demonstrate hyperchromasia , amphophilic cytoplasm and a tendency toward single filing between collagen bundles . nuclear molding may be noted . any myeloid cell line may be represented , including immature neutrophils , eosinophils or basophils . epidermal changes are usually minimal , but may be the most prominent finding in cases such as ours when the biopsy is performed because of the overlying unrelated skin lesion . patients presenting with lc in association with non - melanoma skin cancer have including those with scc and basal cell carcinomas . in our patient , the overlying epidermal changes were diagnostic of ak and it might have been easy to overlook the more important diagnosis of leukemia . dermatopathologists need to remain sensitive to the possibility of a critical diagnosis within the infiltrate underlying a common cutaneous lesion .
we report an 85-year - old female patient who presented with an erythematous keratotic lesion on her temple suspicious of squamous cell carcinoma . 
 histological evaluation revealed actinic keratosis , but the underlying atypical infiltrate contained atypical myeloid forms consistent with acute myelogenous leukemia ( aml ) . upon further questioning 
 , it was determined that the patient had a history of myelodysplastic syndrome . 
 her skin biopsy provided the first evidence of progression to aml . 
 this case serves as an important reminder of the role the dermatopathologist plays in identifying serious systemic disease .