5/23/2017
Disclosure of Relevant
Financial Relationships
Flank mass in a
43-year-old male
USCAP requires that all faculty in a position to
influence or control the content of CME disclose any relevant financial
relationship WITH COMMERCIAL INTERESTS which they or their
Bobbi S. Pritt, MD, MSc
Mayo Clinic
spouse/partner have, or have had, within the past 12 months, which relates
to the content of this educational activity and creates a conflict of interest.
Dr. Bobbi Pritt declares she has no conflicts of interest
to disclose.
History
• 43 year old male presented with tender plaques and nodules
involving his left flank.
• Patient is from the upper Midwestern United States
• No travel outside of the United States.
• His previous medical history is significant for well-controlled
insulin-dependent diabetes.
• An excisional biopsy was performed of one of the nodules
H&E, 20x total magnification
H&E, 40x total magnification
H&E, 100x total magnification
H&E, 200x total magnification
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H&E, 100x total magnification
H&E, 100x total magnification
H&E, 100x total magnification
Masson’s Trichrome, 40x total magnification
Diagnosis?
A.
B.
C.
D.
E.
Helminth, possible roundworm.
Helminth, possible cestode
Not a helminth, foreign body
Not a helminth, fat necrosis
No idea, (ask a colleague!)
Masson’s Trichrome, 100x total magnification
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Lipomembranous Fat Necrosis - General
• A.k.a. membranocystic fat necrosis, lipomembranous
panniculitis
• Initially described in 1974 in bone and subcutaneous tissues
in a case of sudanophilic leukodystrophy of cerebral
hemispheres
• Commonly observed in association with venous insufficiency,
arterial ischemia, diabetes, erythema nodosum, and lupus
• Degenerative process involving mature adipose tissue
• Described from various sites: subcutaneous tissue (usually
lower extremities), breast, testicle, bone marrow, benign and
malignant tumors
• Observed in 0.7% to 9% of inflammatory lesions of
subcutaneous tissues
• More common in women (89% in one case series: Snow et al.)
• Mean age 57 years (range 32-80 years)
Lipomembranous Fat
Necrosis - Morphology
• Cystic (most common; often
microcystic) and non-cystic forms
• Adipocyte necrosis
• Formation of eosinophilic anucleate,
crenated, undulating ribbon-like
membranes.
• Pseudopapillary tufts
• PAS-positive, diastase
resistant membranes
•
Cysts may form complex “Arabesque”
patterns
CD68 and lysozyme
positive
Polycystic lipomembranous osteodysplasia
with sclerosing leukoencephalopathy
(courtesy of Dr. Andrew Folpe)
• Autosomal recessive genetic disorder
• Associated with polymorphisms of 2 genes: TYROBP (DAP12)
and TREM2
• Characterized by fractures (resulting from polycystic osseous
lesions), frontal lobe syndrome, and progressive pre-senile
dementia beginning in the fourth decade.
• Patient: 34 year-old female residing in a skilled nursing facility.
Presented with fractures of the tibia and other bones.
Image courtesy of Lawrence Gibson, MD
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Large Worms in Subcutaneous Tissue
• Roundworms
DDX: Worms
in Tissue
• Dirofilaria species (size in cross-section: 300-350 µm)
• Onchocerca volvulus (150-400 µm diameter)
• Loa loa (~500 µm in diameter)
• Tapeworms
• Taenia solium (cysticercosis)
• Other Taenia sp. (coenurosis)
• Spirometra sp. (sparganosis)
Examples of large roundworms
Anatomy of a Roundworm
Zoonotic Onchocerca species
Dirofilaria species
• Cuticle (including spines, ridges)
• Well-defined musculature
• Internal organs
Image by Lars Westblade, PhD
Image by Ryan Relich, PhD
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Anatomy of a tapeworm larva
• Thin acellular cuticle
• Smooth muscle fibers
• Calcareous corpuscles (small
calcified bodies)
• Depending on the tapeworm:
protoscoleces (immature heads)
with suckers and hooklets, fluidfilled sac
A recent case of lipomembranous fat
necrosis simulating a cestode.
Lipomembranous fat necrosis
Sparganosis
Other examples of tapeworm larvae
A recent case of cysticercosis
Image by Paul Valenstein, MD
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Approach
DDx: plant material
• Measure!
4 mm
1 mm
Approach
Approach
• Measure!
• Look for defined structures
• Measure!
• Look for defined structures
• Cuticle and underlying musculature
LM fat necrosis
No well-defined cuticle
(external ‘lining’
merges with underlying
fibrous connective
tissue
•
•
•
•
Cuticle and underlying musculature
Reproductive or gastrointestinal organs
Eggs
(requires familiarity)
Round worm
Approach
• Measure!
• Look for defined structures
•
•
•
•
Cuticle and underlying musculature
Reproductive or gastrointestinal organs
Eggs
(requires familiarity)
• Special stains
• Masson’s trichrome, PAS, acid fast
• Polarizable?
• Consult (e.g. microbiologist, colleague,
CDC ID Path and DPDx groups)
References
• Nasu et al. A lipid metabolic disease—“membranous lip dystrophy”—an
autopsy case demonstrating numerous peculiar membrane-structures
composed of compound lipid in bone and bone marrow and various
adipose tissues. Acta Pathol Jpn 1973;23:. 539–558
• Segura S, Pujol RM. Lipomembranous fat necrosis of the subcutaneous
tissue. Dermatol Clin 2008;26:509-517.
• Snow JL, Su WPD. Lipomembranous (membranocystic) fat necrosis:
clinicopathologic correlation of 38 cases. Am J Dermatopathol
1996;18(2):151-155.
• Diaz-Cascajo C, Borghi S. Subcutaneous pseudomembranous fat
necrosis: new observations. J Cutan Pathol 2002;29:5-10.
• Pritt BS, Elhosseiny A. Artifacts and pitfalls in infectious disease pathology.
In Pathology of Infectious Diseases, Procop GW and Pritt BS (Eds). 2015
Elsevier: Philadelphia, PA
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